State-of-the-art light sheet microscopes rely on sophisticated control software and hardware to perform the acquisition of gigabytes of image data per second, running over the course of hours and even days. Typically, the microscopes acquire data in a first step, and then only in a second step is this data processed and visualised offline. The delay between data acquisition and assessment wastes time and data storage resources. We present ClearVolume - an free and open-source package for live GPU-based 3D/4D visualisation, tailored to microscopy and volumetric imaging. ClearVolume was designed to easily augment any custom-built lightsheet microscope with realtime 3D/4D visualisation. Key features are the capability to create instant multi-view and multi-colour renderings as well as instant rewind and replay of time-lapse recordings — making live imaging truly live via direct real-time inspection of the specimen imaged.